核壳聚合物负载茂金属催化剂及乙烯聚合

采用半连续种子乳液聚合法,得到了粒径为280 nm左右的以聚甲基丙烯酸甲酯 (PMMA)为核、聚苯乙烯(PS)为壳的PMMA/ PS核壳结构聚合物和以PS为核、PMMA为壳的PS/PMMA核壳结构聚合物.并分别以上述二种核壳聚合物为载体,超临界CO2为溶剂,采用超临界流体浸渍法负载二氯二茂钛(Cp2TiCl2)催化剂,得到PMMA/PS-Cp2TiCl2和PS/PMMA-Cp2TiCl2两种负载型的茂金属催化剂颗粒.通过对二种催化剂颗粒的乙烯淤浆聚合动力学的研究发现,PMMA/PS-Cp2TiCl2催化剂颗粒的聚合反应速度有很大的滞后效应,聚合最大反应速率出现在第9 min,而PS/PMMA-Cp2TiCl2催化剂颗粒动力学行为与Cp2TiCl2催化剂均相聚合相似.

Core-shell Polymer/Cp2TiCl2 Catalysts and their Behaviors in Ethylene Polymerization

Two kinds of core-shell polymers (PMMA/PS and PS/PMMA) were prepared separately by semi-continuous seeded emulsion polymerization. PMMA/PS was prepared by polymerization of styrene in the presence of poly (methyle methacrylate) (PMMA). PS/PMMA was prepared by polymerization of methyl methacrylate (MMA) in the presence of polystyrene (PS). Supercritical CO2 was chosen as the solvent and the Cp2TiCl2catalyst was supported into core-shell polymers through the supercritical fluid impregnation. The supported catalysts were characterized through their behaviors during ethylene slurry polymerization. It was found that, when the PMMA/PS-Cp2TiCl2 catalyst was used, the ethylene polymerization rate has a long induce time (about 9 minutes), while when PS/PMMA-Cp2TiCl2 catalyst was used, the kinetic behavior of ethylene polymerization is similar to that of the homogeneous polymerization catalyzed by Cp2TiCl2. The reason for that is the existence of the chemical bond between Cp2TiCl2 and the ester of PMMA, which makes the active material of the catalyst supports mainly on the PMMA section of the core-shell polymers.